Is there only one possible solution for each board? Today I felt like deriving contradictions was a lot harder today than usual, but I still ended up with the c

Is there only one possible solution for each board? Today I felt like deriving contradictions was a lot harder today than usual, but I still ended up with the correct answers. I think there should be a way to mark dominos as "confirmed" vs "guesses", because not everyone is going to have working memory to remember which tiles laid down are "guesses" for deriving contradictions.